1. Field of Invention
The present invention relates to pressure sensing devices and more particularly a tactile sensing system for sensing where and how much pressure or force is applied at specific locations of an area.
2. Description of the Prior Art
There are many situations in which it would be beneficial to be able to sense and measure the amount of force or pressure that is applied on a surface area, including specific locations in the area where such force or pressure is applied, as well as the magnitude of such force or pressure at each such location. In other words, it would be beneficial to be able to sense pressures at various parts of an area, including magnitudes, on a real time basis, similar to the way a person's nervous system can sense various pressures applied on his or her body. It would also be very desirable to monitor, record, and display an output representation of such forces or pressures on a continuous dynamic basis over a real time continuum.
The potential applications for such a tactilitic sensor system are virtually unlimited, and no attempt will be made to cover or mention even a substantial number of them here. However, an example application is appropriate to illustrate the problem. It is known that too much pressure on a point or location on a person's body sustained over an excessive period of time can cut off circulation and cell nourishment, resulting in pressure sores and even dead tissue. While most of us feel the discomfort and move or shift position to alleviate the problem before damage occurs, such pressure sores or dying tissue can be a significant problem for persons that are immobilized, comatose, disabled to the extent of lacking feeling or muscular control, or unconscious due to general anesthetics during surgery, and the like. Also, the time required for such damage to accrue is relatively short, often as little as several hours. Therefore, while it is often the job of physicians or nursing staff to reposition such persons on a regular basis to relieve problem pressure points, distractions, personnel shortages, and the like can cause such care to be undependable for the person who requires it. A suitable tactilitic monitoring system positioned to provide contact monitoring with the person's body could assist greatly in monitoring the magnitude and duration of pressure points on all locations in a defined area and provide suitable records and alarm or reminders to the nursing or caring personnel. Such a tactilitic system could also be used to indicate or sound a warning or activate a call system if a patient or even a small child gets out of bed, while not giving false alarms from mere motion or changing positions in the bed so long as some part of the system has pressure on it.
Pressure sensitive switches or transducers are, of course, known. For example, U.S. Pat. Nos. 4,484,043 and 4,565,910, issued to J. Musick, et al., and U.S. Pat. Nos. 4,179,692 and 4,295,133 issued to D. Vance, show such pressure switches or transducers used to monitor the presence of a patient in a bed. However, a single, or even several such sensors, cannot function as a true tactilitic sensor system over an area. While a normal initial reaction may be to merely multiply or add more of such sensors or switches to cover the desired area, one soon runs headlong into the pervasive problem of rapidly multiplying control and monitoring complexity that prior to this invention has not been solved in any practical sense. For example, some simple calculations show that even a relatively small area of 4'.times.6' with sensors or pressure transducers positioned every tenth of a foot would amount to over 2,400 switches. A modest 2 m.times.2 m area with sensors spaced about 2 cm apart would have over 10,000 sensors. Even with the possibility of using computers to monitor such a large number of individual switches, the problem would be enormous, not to mention the physical mass of electronic circuits and connections that would be required to connect each switch to a monitoring station. Such system would be either too unwieldy, too fragile, or both, along with a whole host of other problems that prior to this invention made such a tactilitic monitoring system impractical.